The present invention relates to a new and improved construction of apparatus for separation of a stack of folded or bound, multi-sheet printed products, especially newpapers and periodicals, in other words, singling or separating out individual product copies from the stack.
Generally speaking, the product singling apparatus of the present development is of the type comprising a product withdrawal device which engages in each instance at the lowermost product of the stack and withdraws such out of the stack. A retention device serves to retain the remaining products of the stack within the stack until they are singled out of the stack.
According to a prior art apparatus of this type, as exemplified for instance by Swiss Pat. No. 441,389 and the corresponding U.S. Pat. No. 3,446,498, there is provided a to-and-fro moving withdrawal apparatus which frictionally or force-lockingly engages by means of claws at the underside of the lowermost product within the stack and removes the thus seized product. The second lowermost product of the stack is fixedly retained by means of a hook engaging thereat, and therefore, is safeguarded against any undesirable entrainment during the withdrawal of the lowermost product. Apaart from there being required a complicated construction, this state-of-the-art equipment is afflicted with further drawbacks since there is present the danger of damaging the products by the claws of the withdrawal device and the retention hooks. With this prior art withdrawal device it is not possible to remove the momentary lowermost product of an upright stack from below the other products located thereover. Therefore, the stack must be tilted prior to the product singling or separation operation, so that the lowermost product comes to lie in a plane which encloses an acute angle with the horizontal. The products are then pulled out by the withdrawal device in such plane. This tilting of the stack necessitates that there be provided an appropriate mechanism for this purpose. Additionally, with the prior art destacking apparatus under discussion there is not insured for a faultless withdrawal of thick products or product copies.
Other constructions of apparatus for separating printed products or sheets of paper have been disclosed in U.S. Pat. Nos. 3,690,645; 4,127,262; 3,045,867; 3,785,523; and British Pat. Nos. 1,363,859 and 1,294,069.